Though each tracked phone is identified by a unique ID rather than a person’s name or phone number, the millions of location points collected by the apps are “accurate to within a few yards” and can reveal a person’s daily movements “in startling detail,” The Times said.

Using a database that tracks the location data of more than 1 million phones in the New York area, The Times was able to identify a person whose location was being relayed to companies via her smartphone app.

The Times reported:

“At least 75 companies receive anonymous, precise location data from apps whose users enable location services to get local news and weather or other information, The Times found. Several of those businesses claim to track up to 200 million mobile devices in the United States – about half those in use last year …

“But those with access to the raw data – including employees or clients – could still identify a person without consent. They could follow someone they knew, by pinpointing a phone that regularly spent time at that person’s home address. Or, working in reverse, they could attach a name to an anonymous dot, by seeing where the device spent nights and using public records to figure out who lived there.”

Apps will often ask smartphone users to enable location-tracking services for better functionality, like those that provide GPS navigation, weather information, or food recommendations. But The Times said the privacy policies that many people accept without thinking twice were often “incomplete or misleading,” adding that companies could use these permissions to sell your location data.

“These companies sell, use or analyse the data to cater to advertisers, retail outlets and even hedge funds seeking insights into consumer behaviour,” the Times story said.

But the good news is you do have some control. You can adjust the settings for individual apps to stop them from tracking your location, though turning off location services for some apps may limit their capabilities or render them unworkable.

The easiest way to turn off location tracking for each app is through your device’s privacy settings – here’s how to do that:

If you have an iOS device, location-tracking settings can be found in Settings under “Privacy.”

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Next, select “Location Services” …

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… where you’ll find the location-data permissions for every app on your device.

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Under each app, you can select the level of access to your location data you want to give: whether you want the app to always have access even when it isn’t being used, or only while you’re using it, or never. Some apps explain what they use your location for.

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If you own an Android device, location tracking is in Settings under “Security & location.”

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Under “Privacy,” select “Location” …

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… then “App-level permissions.”

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For Android, you can’t toggle among options like on iOS devices — you can choose either to grant an app permission to access your location, or take away its access altogether. But you could always turn off location sharing and then re-enable it when you want to use the app.